org.mortbay.cometd
Class CometdServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          org.mortbay.cometd.CometdServlet

All Implemented Interfaces:

Serializable, Servlet, ServletConfig

public class CometdServlet
extends HttpServlet

Cometd Filter Servlet implementing the Bayeux protocol. The Servlet can be initialized with a json file mapping channels to DataFilter definitions. The servlet init parameter "filters" should point to a webapplication resource containing a JSON array of filter definitions. For example:

 [
   { 
     "channels": "/**",
     "class"   : "org.mortbay.cometd.filter.NoMarkupFilter",
     "init"    : {}
   }
 ]
 

The init parameter "timeout" specifies the poll timeout in milliseconds (default 45000). The init parameter "multiTimeout" specifies the poll timeout if multiple polls are detected from the same browser (default 0 - disable browser detection).

Author:

gregw

See Also:

Bayeux}, ChannelPattern}, Serialized Form

Field Summary

static String	BROWSER_ID
static String	CLIENT_ATTR
static String	MESSAGE_PARAM
static String	ORG_MORTBAY_BAYEUX
static String	TUNNEL_INIT_PARAM

Constructor Summary

CometdServlet()

Method Summary

protected void	doGet(HttpServletRequest req, HttpServletResponse resp) Called by the server (via the service method) to allow a servlet to handle a GET request.
protected void	doPost(HttpServletRequest req, HttpServletResponse resp) Called by the server (via the service method) to allow a servlet to handle a POST request.
void	init() A convenience method which can be overridden so that there's no need to call super.init(config).
protected void	service(HttpServletRequest req, HttpServletResponse resp) Receives standard HTTP requests from the public service method and dispatches them to the doXXX methods defined in this class.

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPut, doTrace, getLastModified, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ORG_MORTBAY_BAYEUX

public static final String ORG_MORTBAY_BAYEUX

See Also:

Constant Field Values

CLIENT_ATTR

public static final String CLIENT_ATTR

See Also:

Constant Field Values

MESSAGE_PARAM

public static final String MESSAGE_PARAM

See Also:

Constant Field Values

TUNNEL_INIT_PARAM

public static final String TUNNEL_INIT_PARAM

See Also:

Constant Field Values

BROWSER_ID

public static final String BROWSER_ID

See Also:

Constant Field Values

Constructor Detail

CometdServlet

public CometdServlet()

Method Detail

init

public void init()
          throws ServletException

Description copied from class: GenericServlet

A convenience method which can be overridden so that there's no need to call super.init(config).

Instead of overriding GenericServlet.init(ServletConfig), simply override this method and it will be called by GenericServlet.init(ServletConfig config). The ServletConfig object can still be retrieved via GenericServlet.getServletConfig().

Overrides:

init in class GenericServlet

Throws:

ServletException - if an exception occurs that interrupts the servlet's normal operation

service

protected void service(HttpServletRequest req,
                       HttpServletResponse resp)
                throws ServletException,
                       IOException

Description copied from class: HttpServlet

Receives standard HTTP requests from the public service method and dispatches them to the doXXX methods defined in this class. This method is an HTTP-specific version of the Servlet.service(javax.servlet.ServletRequest, javax.servlet.ServletResponse) method. There's no need to override this method.

Overrides:

service in class HttpServlet

Parameters:

req - the HttpServletRequest object that contains the request the client made of the servlet

resp - the HttpServletResponse object that contains the response the servlet returns to the client

Throws:

ServletException - if the HTTP request cannot be handled

IOException - if an input or output error occurs while the servlet is handling the HTTP request

See Also:

Servlet.service(javax.servlet.ServletRequest, javax.servlet.ServletResponse)

doPost

protected void doPost(HttpServletRequest req,
                      HttpServletResponse resp)
               throws ServletException,
                      IOException

Description copied from class: HttpServlet

Called by the server (via the service method) to allow a servlet to handle a POST request. The HTTP POST method allows the client to send data of unlimited length to the Web server a single time and is useful when posting information such as credit card numbers.

When overriding this method, read the request data, write the response headers, get the response's writer or output stream object, and finally, write the response data. It's best to include content type and encoding. When using a PrintWriter object to return the response, set the content type before accessing the PrintWriter object.

The servlet container must write the headers before committing the response, because in HTTP the headers must be sent before the response body.

Where possible, set the Content-Length header (with the ServletResponse.setContentLength(int) method), to allow the servlet container to use a persistent connection to return its response to the client, improving performance. The content length is automatically set if the entire response fits inside the response buffer.

When using HTTP 1.1 chunked encoding (which means that the response has a Transfer-Encoding header), do not set the Content-Length header.

This method does not need to be either safe or idempotent. Operations requested through POST can have side effects for which the user can be held accountable, for example, updating stored data or buying items online.

If the HTTP POST request is incorrectly formatted, doPost returns an HTTP "Bad Request" message.

Overrides:

doPost in class HttpServlet

Parameters:

req - an HttpServletRequest object that contains the request the client has made of the servlet

resp - an HttpServletResponse object that contains the response the servlet sends to the client

Throws:

ServletException - if the request for the POST could not be handled

IOException - if an input or output error is detected when the servlet handles the request

See Also:

ServletOutputStream, ServletResponse.setContentType(java.lang.String)

doGet

protected void doGet(HttpServletRequest req,
                     HttpServletResponse resp)
              throws ServletException,
                     IOException

Description copied from class: HttpServlet

Called by the server (via the service method) to allow a servlet to handle a GET request.

Overriding this method to support a GET request also automatically supports an HTTP HEAD request. A HEAD request is a GET request that returns no body in the response, only the request header fields.

When overriding this method, read the request data, write the response headers, get the response's writer or output stream object, and finally, write the response data. It's best to include content type and encoding. When using a PrintWriter object to return the response, set the content type before accessing the PrintWriter object.

The servlet container must write the headers before committing the response, because in HTTP the headers must be sent before the response body.

Where possible, set the Content-Length header (with the ServletResponse.setContentLength(int) method), to allow the servlet container to use a persistent connection to return its response to the client, improving performance. The content length is automatically set if the entire response fits inside the response buffer.

When using HTTP 1.1 chunked encoding (which means that the response has a Transfer-Encoding header), do not set the Content-Length header.

The GET method should be safe, that is, without any side effects for which users are held responsible. For example, most form queries have no side effects. If a client request is intended to change stored data, the request should use some other HTTP method.

The GET method should also be idempotent, meaning that it can be safely repeated. Sometimes making a method safe also makes it idempotent. For example, repeating queries is both safe and idempotent, but buying a product online or modifying data is neither safe nor idempotent.

If the request is incorrectly formatted, doGet returns an HTTP "Bad Request" message.

Overrides:

doGet in class HttpServlet

Parameters:

req - an HttpServletRequest object that contains the request the client has made of the servlet

resp - an HttpServletResponse object that contains the response the servlet sends to the client

Throws:

ServletException - if the request for the GET could not be handled

IOException - if an input or output error is detected when the servlet handles the GET request

See Also:

ServletResponse.setContentType(java.lang.String)